Preheat the oven to 425°F
Pat the Cornish game hens dry with paper towels
Remove any giblets from the cavity
Place the hens on a baking sheet or in a roasting pan
Rub the hens with olive oil or melted butter
Season the hens with salt, pepper, garlic powder, and herbs
Stuff the cavities with lemon, garlic, onion, or fresh herbs if desired
Tie the legs together with kitchen twine if desired
Roast the hens for 45 to 60 minutes
Baste the hens once or twice during cooking if desired
Check that the internal temperature reaches 165°F in the thickest part of the thigh
Let the hens rest for 10 minutes before serving
Serve whole or halved with your choice of side dishes